1. Field of the Invention
The present invention relates to a solid xylylenediamine in a container, a production method thereof, and a method for storing xylylenediamine. The solid xylylenediamine in a container of the invention is quite stable on storing, and therefore, industrially useful. The xylylenediamine is a useful compound as a raw material for polyamide resins, curing agents, etc. and as an intermediate material for isocyanines compounds, etc.
2. Description of the Prior Art
Amines are liable to undergo the change of their quality by light, heat, oxygen, etc. and are well known to suffer from deterioration such as discoloration, change into odorous substance, etc. during their storage. Unlike aromatic amines such as diaminotoluene compounds and apliphatic amines such as hexamethylenediamine and isophoronediamine, the xylylenediamine structurally belongs to benzylamines. Therefore, the xylylenediamine is extremely susceptible to autoxidation and deammodation as compared with the aromatic amines and the aliphatic amines. Conventionally, the xylylenediamine has been stored in a sealed container having its inner air replaced by an inert gas such as nitrogen gas while being kept apart from the influence of light, heat, etc. In spite of such efforts, a satisfactory result is still not obtained.
As to the technique for stably storing the xylylenediamine, JP 46-21857 B discloses to add an unsaturated compound having a terminal double bond such as 1-butene, 1-hexene and styrene. However, the proposed method lowers the purity of final products because of inclusion of the additive. Alternatively, some disadvantages attributable to the added unsaturated compound may be caused during the use of final products.
JP 10-81651 A teaches that the generation of ammonia odor due to the degradation during storage can be prevented by storing a liquid aliphatic polyamine in a sealed container under a substantially oxygen-free condition. According to the examination made by the inventors, however, the xylylenediamine after storage was degraded and discolored even when the xylylenediamine was stored in drum cans and 20-L cans, which are industrially generally used as containers for storing the xylylenediamine, after replacing the inner atmosphere thereof by nitrogen in advance of charging the xylylenediamine into the containers under a flow of nitrogen. It seems that the “substantially oxygen-free condition” taught by JP 10-81651 A was not actually attained because oxygen could not be removed sufficiently by the nitrogen-replacement methods which have been employed in industrial productions to achieve the substantially oxygen-free condition. In fact, in the examination made by the inventors on the storage of xylylenediamine in 20-L cans, the oxygen content of the headspace in the 20-L cans was about 500 to 2000 ppm, although the 20-L cans had been purged with nitrogen in advance of changing the xylylenediamine under a flow of nitrogen. In addition, the oxygen content of the headspace in the 20-L cans after storage was higher than just after completing the charge of the xylylenediamine. This seems to be due to the penetration of air into the cans during storage. Therefore, to store the xylylenediamine under the substantially oxygen-free condition, special cares must be taken during the charge and in selecting the containers and packings so as to prevent the penetration of oxygen into the containers. However, the techniques usually employed in industrial process have been insufficient for achieving the substantially oxygen-free condition.
Not related to the storage of aromatic ring-containing aliphatic amine such as xylylenediamine, JP 2002-193897 A teaches that the quality of aromatic amines can be maintained without discoloration by storing under a sealed condition in the presence of an oxygen absorbing agent and a desiccant. Generally, the oxygen absorbing agent needs moisture to exhibit its function. Therefore, there will be a deterioration of quality due to the moisture entered into the amines. To prevent this problem, the desiccant is combinedly used. However, the use of desiccant makes it difficult to maintain the moisture content at a sufficient level for allowing the oxygen absorbing agent to exhibit its function. High-purity amines are extremely hygroscopic and have a moisture-absorbing speed comparable to common desiccants such as silica gel, activated carbon, molecular sieve and anhydrous calcium chloride. Therefore, it is practically impossible to completely absorb the moisture by the desiccant, namely, to completely prevent the moisture from entering into the amines.
In addition, since the pressure of headspace in the container is reduced by the absorption of oxygen, the proposed method has another problem such as deformation of container. To solve this problem, the use of a pressure container that is able to withstand the negative pressure is needed. The packing for the closure of container is also required to have gas-barrier properties to maintain a hermetic seal. Therefore, the containers usable in the proposed method are of a type not applicable to wide purposes.